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<link rel="import" href="../mixins/mutable-data.html">

<script>
(function() {
  'use strict';

  let mutablePropertyChange;
  /** @suppress {missingProperties} */
  (() => {
    mutablePropertyChange = Polymer.MutableData._mutablePropertyChange;
  })();

  /**
   * Legacy element behavior to skip strict dirty-checking for objects and arrays,
   * (always consider them to be "dirty") for use on legacy API Polymer elements.
   *
   * By default, `Polymer.PropertyEffects` performs strict dirty checking on
   * objects, which means that any deep modifications to an object or array will
   * not be propagated unless "immutable" data patterns are used (i.e. all object
   * references from the root to the mutation were changed).
   *
   * Polymer also provides a proprietary data mutation and path notification API
   * (e.g. `notifyPath`, `set`, and array mutation API's) that allow efficient
   * mutation and notification of deep changes in an object graph to all elements
   * bound to the same object graph.
   *
   * In cases where neither immutable patterns nor the data mutation API can be
   * used, applying this mixin will cause Polymer to skip dirty checking for
   * objects and arrays (always consider them to be "dirty").  This allows a
   * user to make a deep modification to a bound object graph, and then either
   * simply re-set the object (e.g. `this.items = this.items`) or call `notifyPath`
   * (e.g. `this.notifyPath('items')`) to update the tree.  Note that all
   * elements that wish to be updated based on deep mutations must apply this
   * mixin or otherwise skip strict dirty checking for objects/arrays.
   *
   * In order to make the dirty check strategy configurable, see
   * `Polymer.OptionalMutableDataBehavior`.
   *
   * Note, the performance characteristics of propagating large object graphs
   * will be worse as opposed to using strict dirty checking with immutable
   * patterns or Polymer's path notification API.
   *
   * @polymerBehavior
   * @memberof Polymer
   * @summary Behavior to skip strict dirty-checking for objects and
   *   arrays
   */
  Polymer.MutableDataBehavior = {

    /**
     * Overrides `Polymer.PropertyEffects` to provide option for skipping
     * strict equality checking for Objects and Arrays.
     *
     * This method pulls the value to dirty check against from the `__dataTemp`
     * cache (rather than the normal `__data` cache) for Objects.  Since the temp
     * cache is cleared at the end of a turn, this implementation allows
     * side-effects of deep object changes to be processed by re-setting the
     * same object (using the temp cache as an in-turn backstop to prevent
     * cycles due to 2-way notification).
     *
     * @param {string} property Property name
     * @param {*} value New property value
     * @param {*} old Previous property value
     * @return {boolean} Whether the property should be considered a change
     * @protected
     */
    _shouldPropertyChange(property, value, old) {
      return mutablePropertyChange(this, property, value, old, true);
    }
  };

  /**
   * Legacy element behavior to add the optional ability to skip strict
   * dirty-checking for objects and arrays (always consider them to be
   * "dirty") by setting a `mutable-data` attribute on an element instance.
   *
   * By default, `Polymer.PropertyEffects` performs strict dirty checking on
   * objects, which means that any deep modifications to an object or array will
   * not be propagated unless "immutable" data patterns are used (i.e. all object
   * references from the root to the mutation were changed).
   *
   * Polymer also provides a proprietary data mutation and path notification API
   * (e.g. `notifyPath`, `set`, and array mutation API's) that allow efficient
   * mutation and notification of deep changes in an object graph to all elements
   * bound to the same object graph.
   *
   * In cases where neither immutable patterns nor the data mutation API can be
   * used, applying this mixin will allow Polymer to skip dirty checking for
   * objects and arrays (always consider them to be "dirty").  This allows a
   * user to make a deep modification to a bound object graph, and then either
   * simply re-set the object (e.g. `this.items = this.items`) or call `notifyPath`
   * (e.g. `this.notifyPath('items')`) to update the tree.  Note that all
   * elements that wish to be updated based on deep mutations must apply this
   * mixin or otherwise skip strict dirty checking for objects/arrays.
   *
   * While this behavior adds the ability to forgo Object/Array dirty checking,
   * the `mutableData` flag defaults to false and must be set on the instance.
   *
   * Note, the performance characteristics of propagating large object graphs
   * will be worse by relying on `mutableData: true` as opposed to using
   * strict dirty checking with immutable patterns or Polymer's path notification
   * API.
   *
   * @polymerBehavior
   * @memberof Polymer
   * @summary Behavior to optionally skip strict dirty-checking for objects and
   *   arrays
   */
  Polymer.OptionalMutableDataBehavior = {

    properties: {
      /**
       * Instance-level flag for configuring the dirty-checking strategy
       * for this element.  When true, Objects and Arrays will skip dirty
       * checking, otherwise strict equality checking will be used.
       */
      mutableData: Boolean
    },

    /**
     * Overrides `Polymer.PropertyEffects` to skip strict equality checking
     * for Objects and Arrays.
     *
     * Pulls the value to dirty check against from the `__dataTemp` cache
     * (rather than the normal `__data` cache) for Objects.  Since the temp
     * cache is cleared at the end of a turn, this implementation allows
     * side-effects of deep object changes to be processed by re-setting the
     * same object (using the temp cache as an in-turn backstop to prevent
     * cycles due to 2-way notification).
     *
     * @param {string} property Property name
     * @param {*} value New property value
     * @param {*} old Previous property value
     * @return {boolean} Whether the property should be considered a change
     * @this {this}
     * @protected
     */
    _shouldPropertyChange(property, value, old) {
      return mutablePropertyChange(this, property, value, old, this.mutableData);
    }
  };

})();

</script>
